The invention belongs to the technical field of metal cutting processing. The technical scheme of the invention is to provide a fully-synthetic cutting fluid for metal processing, and the fully-synthetic cutting fluid is composed of the following raw materials in parts by mass: 10-35 parts of first deionized water, 1-5 parts of linear-chain dodecanedioic acid, 1-6 parts of boric acid, 0.1-0.5 partof benzotriazole, 2-8 parts of monoethanolamine, 5-20 parts of diethanolamine, 3-6 parts of D1550 fatty acid, 1-3 parts of ricinoleic acid, 2-7 parts of ricinoleic acid tetramer, 1.6-5.2 parts of isononanoic acid, 1.2-4.3 parts of caprylic-capric acid blend, 2-2.5 parts of dicyclohexylamine, 2-4.3 parts of fatty alcohol, 1-2.6 parts of polyolefin (sixteen carbons), 1-2 parts of isomeric octadecanol, 10-70 parts of second deionized water, 1-3 parts of bactericide and 0.1-1 part of defoaming agent. The fully-synthetic cutting fluid has the beneficial effects that the fully-synthetic cutting fluid for metal processing is low in using cost, good in lubricating properties and long in service life, and the phenomenon that a diluent goes bad to generate peculiar smell is not easily caused.